initial_commit

1 files changed, 997 insertions, 0 deletions

diff --git a/fs/libfs.c b/fs/libfs.c
new file mode 100644
index 00000000..275ca474
--- /dev/null
+++ b/fs/libfs.c
@@ -0,0 +1,997 @@
+/*
+ *	fs/libfs.c
+ *	Library for filesystems writers.
+ */
+
+#include <linux/module.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/mount.h>
+#include <linux/vfs.h>
+#include <linux/quotaops.h>
+#include <linux/mutex.h>
+#include <linux/exportfs.h>
+#include <linux/writeback.h>
+#include <linux/buffer_head.h>
+
+#include <asm/uaccess.h>
+
+static inline int simple_positive(struct dentry *dentry)
+{
+	return dentry->d_inode && !d_unhashed(dentry);
+}
+
+int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
+		   struct kstat *stat)
+{
+	struct inode *inode = dentry->d_inode;
+	generic_fillattr(inode, stat);
+	stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
+	return 0;
+}
+
+int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	buf->f_type = dentry->d_sb->s_magic;
+	buf->f_bsize = PAGE_CACHE_SIZE;
+	buf->f_namelen = NAME_MAX;
+	return 0;
+}
+
+/*
+ * Retaining negative dentries for an in-memory filesystem just wastes
+ * memory and lookup time: arrange for them to be deleted immediately.
+ */
+static int simple_delete_dentry(const struct dentry *dentry)
+{
+	return 1;
+}
+
+/*
+ * Lookup the data. This is trivial - if the dentry didn't already
+ * exist, we know it is negative.  Set d_op to delete negative dentries.
+ */
+struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
+{
+	static const struct dentry_operations simple_dentry_operations = {
+		.d_delete = simple_delete_dentry,
+	};
+
+	if (dentry->d_name.len > NAME_MAX)
+		return ERR_PTR(-ENAMETOOLONG);
+	d_set_d_op(dentry, &simple_dentry_operations);
+	d_add(dentry, NULL);
+	return NULL;
+}
+
+int dcache_dir_open(struct inode *inode, struct file *file)
+{
+	static struct qstr cursor_name = {.len = 1, .name = "."};
+
+	file->private_data = d_alloc(file->f_path.dentry, &cursor_name);
+
+	return file->private_data ? 0 : -ENOMEM;
+}
+
+int dcache_dir_close(struct inode *inode, struct file *file)
+{
+	dput(file->private_data);
+	return 0;
+}
+
+loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
+{
+	struct dentry *dentry = file->f_path.dentry;
+	mutex_lock(&dentry->d_inode->i_mutex);
+	switch (origin) {
+		case 1:
+			offset += file->f_pos;
+		case 0:
+			if (offset >= 0)
+				break;
+		default:
+			mutex_unlock(&dentry->d_inode->i_mutex);
+			return -EINVAL;
+	}
+	if (offset != file->f_pos) {
+		file->f_pos = offset;
+		if (file->f_pos >= 2) {
+			struct list_head *p;
+			struct dentry *cursor = file->private_data;
+			loff_t n = file->f_pos - 2;
+
+			spin_lock(&dentry->d_lock);
+			/* d_lock not required for cursor */
+			list_del(&cursor->d_u.d_child);
+			p = dentry->d_subdirs.next;
+			while (n && p != &dentry->d_subdirs) {
+				struct dentry *next;
+				next = list_entry(p, struct dentry, d_u.d_child);
+				spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
+				if (simple_positive(next))
+					n--;
+				spin_unlock(&next->d_lock);
+				p = p->next;
+			}
+			list_add_tail(&cursor->d_u.d_child, p);
+			spin_unlock(&dentry->d_lock);
+		}
+	}
+	mutex_unlock(&dentry->d_inode->i_mutex);
+	return offset;
+}
+
+/* Relationship between i_mode and the DT_xxx types */
+static inline unsigned char dt_type(struct inode *inode)
+{
+	return (inode->i_mode >> 12) & 15;
+}
+
+/*
+ * Directory is locked and all positive dentries in it are safe, since
+ * for ramfs-type trees they can't go away without unlink() or rmdir(),
+ * both impossible due to the lock on directory.
+ */
+
+int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
+{
+	struct dentry *dentry = filp->f_path.dentry;
+	struct dentry *cursor = filp->private_data;
+	struct list_head *p, *q = &cursor->d_u.d_child;
+	ino_t ino;
+	int i = filp->f_pos;
+
+	switch (i) {
+		case 0:
+			ino = dentry->d_inode->i_ino;
+			if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
+				break;
+			filp->f_pos++;
+			i++;
+			/* fallthrough */
+		case 1:
+			ino = parent_ino(dentry);
+			if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
+				break;
+			filp->f_pos++;
+			i++;
+			/* fallthrough */
+		default:
+			spin_lock(&dentry->d_lock);
+			if (filp->f_pos == 2)
+				list_move(q, &dentry->d_subdirs);
+
+			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
+				struct dentry *next;
+				next = list_entry(p, struct dentry, d_u.d_child);
+				spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
+				if (!simple_positive(next)) {
+					spin_unlock(&next->d_lock);
+					continue;
+				}
+
+				spin_unlock(&next->d_lock);
+				spin_unlock(&dentry->d_lock);
+				if (filldir(dirent, next->d_name.name, 
+					    next->d_name.len, filp->f_pos, 
+					    next->d_inode->i_ino, 
+					    dt_type(next->d_inode)) < 0)
+					return 0;
+				spin_lock(&dentry->d_lock);
+				spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
+				/* next is still alive */
+				list_move(q, p);
+				spin_unlock(&next->d_lock);
+				p = q;
+				filp->f_pos++;
+			}
+			spin_unlock(&dentry->d_lock);
+	}
+	return 0;
+}
+
+ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
+{
+	return -EISDIR;
+}
+
+const struct file_operations simple_dir_operations = {
+	.open		= dcache_dir_open,
+	.release	= dcache_dir_close,
+	.llseek		= dcache_dir_lseek,
+	.read		= generic_read_dir,
+	.readdir	= dcache_readdir,
+	.fsync		= noop_fsync,
+};
+
+const struct inode_operations simple_dir_inode_operations = {
+	.lookup		= simple_lookup,
+};
+
+static const struct super_operations simple_super_operations = {
+	.statfs		= simple_statfs,
+};
+
+/*
+ * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
+ * will never be mountable)
+ */
+struct dentry *mount_pseudo(struct file_system_type *fs_type, char *name,
+	const struct super_operations *ops,
+	const struct dentry_operations *dops, unsigned long magic)
+{
+	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
+	struct dentry *dentry;
+	struct inode *root;
+	struct qstr d_name = {.name = name, .len = strlen(name)};
+
+	if (IS_ERR(s))
+		return ERR_CAST(s);
+
+	s->s_flags = MS_NOUSER;
+	s->s_maxbytes = MAX_LFS_FILESIZE;
+	s->s_blocksize = PAGE_SIZE;
+	s->s_blocksize_bits = PAGE_SHIFT;
+	s->s_magic = magic;
+	s->s_op = ops ? ops : &simple_super_operations;
+	s->s_time_gran = 1;
+	root = new_inode(s);
+	if (!root)
+		goto Enomem;
+	/*
+	 * since this is the first inode, make it number 1. New inodes created
+	 * after this must take care not to collide with it (by passing
+	 * max_reserved of 1 to iunique).
+	 */
+	root->i_ino = 1;
+	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
+	root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
+	dentry = d_alloc(NULL, &d_name);
+	if (!dentry) {
+		iput(root);
+		goto Enomem;
+	}
+	dentry->d_sb = s;
+	dentry->d_parent = dentry;
+	d_instantiate(dentry, root);
+	s->s_root = dentry;
+	s->s_d_op = dops;
+	s->s_flags |= MS_ACTIVE;
+	return dget(s->s_root);
+
+Enomem:
+	deactivate_locked_super(s);
+	return ERR_PTR(-ENOMEM);
+}
+
+int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = old_dentry->d_inode;
+
+	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
+	inc_nlink(inode);
+	ihold(inode);
+	dget(dentry);
+	d_instantiate(dentry, inode);
+	return 0;
+}
+
+int simple_empty(struct dentry *dentry)
+{
+	struct dentry *child;
+	int ret = 0;
+
+	spin_lock(&dentry->d_lock);
+	list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
+		spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
+		if (simple_positive(child)) {
+			spin_unlock(&child->d_lock);
+			goto out;
+		}
+		spin_unlock(&child->d_lock);
+	}
+	ret = 1;
+out:
+	spin_unlock(&dentry->d_lock);
+	return ret;
+}
+
+int simple_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = dentry->d_inode;
+
+	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
+	drop_nlink(inode);
+	dput(dentry);
+	return 0;
+}
+
+int simple_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	if (!simple_empty(dentry))
+		return -ENOTEMPTY;
+
+	drop_nlink(dentry->d_inode);
+	simple_unlink(dir, dentry);
+	drop_nlink(dir);
+	return 0;
+}
+
+int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
+		struct inode *new_dir, struct dentry *new_dentry)
+{
+	struct inode *inode = old_dentry->d_inode;
+	int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
+
+	if (!simple_empty(new_dentry))
+		return -ENOTEMPTY;
+
+	if (new_dentry->d_inode) {
+		simple_unlink(new_dir, new_dentry);
+		if (they_are_dirs)
+			drop_nlink(old_dir);
+	} else if (they_are_dirs) {
+		drop_nlink(old_dir);
+		inc_nlink(new_dir);
+	}
+
+	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
+		new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
+
+	return 0;
+}
+
+/**
+ * simple_setattr - setattr for simple filesystem
+ * @dentry: dentry
+ * @iattr: iattr structure
+ *
+ * Returns 0 on success, -error on failure.
+ *
+ * simple_setattr is a simple ->setattr implementation without a proper
+ * implementation of size changes.
+ *
+ * It can either be used for in-memory filesystems or special files
+ * on simple regular filesystems.  Anything that needs to change on-disk
+ * or wire state on size changes needs its own setattr method.
+ */
+int simple_setattr(struct dentry *dentry, struct iattr *iattr)
+{
+	struct inode *inode = dentry->d_inode;
+	int error;
+
+	WARN_ON_ONCE(inode->i_op->truncate);
+
+	error = inode_change_ok(inode, iattr);
+	if (error)
+		return error;
+
+	if (iattr->ia_valid & ATTR_SIZE)
+		truncate_setsize(inode, iattr->ia_size);
+	setattr_copy(inode, iattr);
+	mark_inode_dirty(inode);
+	return 0;
+}
+EXPORT_SYMBOL(simple_setattr);
+
+int simple_readpage(struct file *file, struct page *page)
+{
+	clear_highpage(page);
+	flush_dcache_page(page);
+	SetPageUptodate(page);
+	unlock_page(page);
+	return 0;
+}
+
+int simple_write_begin(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned flags,
+			struct page **pagep, void **fsdata)
+{
+	struct page *page;
+	pgoff_t index;
+
+	index = pos >> PAGE_CACHE_SHIFT;
+
+	page = grab_cache_page_write_begin(mapping, index, flags);
+	if (!page)
+		return -ENOMEM;
+
+	*pagep = page;
+
+	if (!PageUptodate(page) && (len != PAGE_CACHE_SIZE)) {
+		unsigned from = pos & (PAGE_CACHE_SIZE - 1);
+
+		zero_user_segments(page, 0, from, from + len, PAGE_CACHE_SIZE);
+	}
+	return 0;
+}
+
+/**
+ * simple_write_end - .write_end helper for non-block-device FSes
+ * @available: See .write_end of address_space_operations
+ * @file: 		"
+ * @mapping: 		"
+ * @pos: 		"
+ * @len: 		"
+ * @copied: 		"
+ * @page: 		"
+ * @fsdata: 		"
+ *
+ * simple_write_end does the minimum needed for updating a page after writing is
+ * done. It has the same API signature as the .write_end of
+ * address_space_operations vector. So it can just be set onto .write_end for
+ * FSes that don't need any other processing. i_mutex is assumed to be held.
+ * Block based filesystems should use generic_write_end().
+ * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
+ * is not called, so a filesystem that actually does store data in .write_inode
+ * should extend on what's done here with a call to mark_inode_dirty() in the
+ * case that i_size has changed.
+ */
+int simple_write_end(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned copied,
+			struct page *page, void *fsdata)
+{
+	struct inode *inode = page->mapping->host;
+	loff_t last_pos = pos + copied;
+
+	/* zero the stale part of the page if we did a short copy */
+	if (copied < len) {
+		unsigned from = pos & (PAGE_CACHE_SIZE - 1);
+
+		zero_user(page, from + copied, len - copied);
+	}
+
+	if (!PageUptodate(page))
+		SetPageUptodate(page);
+	/*
+	 * No need to use i_size_read() here, the i_size
+	 * cannot change under us because we hold the i_mutex.
+	 */
+	if (last_pos > inode->i_size)
+		i_size_write(inode, last_pos);
+
+	set_page_dirty(page);
+	unlock_page(page);
+	page_cache_release(page);
+
+	return copied;
+}
+
+/*
+ * the inodes created here are not hashed. If you use iunique to generate
+ * unique inode values later for this filesystem, then you must take care
+ * to pass it an appropriate max_reserved value to avoid collisions.
+ */
+int simple_fill_super(struct super_block *s, unsigned long magic,
+		      struct tree_descr *files)
+{
+	struct inode *inode;
+	struct dentry *root;
+	struct dentry *dentry;
+	int i;
+
+	s->s_blocksize = PAGE_CACHE_SIZE;
+	s->s_blocksize_bits = PAGE_CACHE_SHIFT;
+	s->s_magic = magic;
+	s->s_op = &simple_super_operations;
+	s->s_time_gran = 1;
+
+	inode = new_inode(s);
+	if (!inode)
+		return -ENOMEM;
+	/*
+	 * because the root inode is 1, the files array must not contain an
+	 * entry at index 1
+	 */
+	inode->i_ino = 1;
+	inode->i_mode = S_IFDIR | 0755;
+	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+	inode->i_op = &simple_dir_inode_operations;
+	inode->i_fop = &simple_dir_operations;
+	inode->i_nlink = 2;
+	root = d_alloc_root(inode);
+	if (!root) {
+		iput(inode);
+		return -ENOMEM;
+	}
+	for (i = 0; !files->name || files->name[0]; i++, files++) {
+		if (!files->name)
+			continue;
+
+		/* warn if it tries to conflict with the root inode */
+		if (unlikely(i == 1))
+			printk(KERN_WARNING "%s: %s passed in a files array"
+				"with an index of 1!\n", __func__,
+				s->s_type->name);
+
+		dentry = d_alloc_name(root, files->name);
+		if (!dentry)
+			goto out;
+		inode = new_inode(s);
+		if (!inode)
+			goto out;
+		inode->i_mode = S_IFREG | files->mode;
+		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+		inode->i_fop = files->ops;
+		inode->i_ino = i;
+		d_add(dentry, inode);
+	}
+	s->s_root = root;
+	return 0;
+out:
+	d_genocide(root);
+	dput(root);
+	return -ENOMEM;
+}
+
+static DEFINE_SPINLOCK(pin_fs_lock);
+
+int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
+{
+	struct vfsmount *mnt = NULL;
+	spin_lock(&pin_fs_lock);
+	if (unlikely(!*mount)) {
+		spin_unlock(&pin_fs_lock);
+		mnt = vfs_kern_mount(type, 0, type->name, NULL);
+		if (IS_ERR(mnt))
+			return PTR_ERR(mnt);
+		spin_lock(&pin_fs_lock);
+		if (!*mount)
+			*mount = mnt;
+	}
+	mntget(*mount);
+	++*count;
+	spin_unlock(&pin_fs_lock);
+	mntput(mnt);
+	return 0;
+}
+
+void simple_release_fs(struct vfsmount **mount, int *count)
+{
+	struct vfsmount *mnt;
+	spin_lock(&pin_fs_lock);
+	mnt = *mount;
+	if (!--*count)
+		*mount = NULL;
+	spin_unlock(&pin_fs_lock);
+	mntput(mnt);
+}
+
+/**
+ * simple_read_from_buffer - copy data from the buffer to user space
+ * @to: the user space buffer to read to
+ * @count: the maximum number of bytes to read
+ * @ppos: the current position in the buffer
+ * @from: the buffer to read from
+ * @available: the size of the buffer
+ *
+ * The simple_read_from_buffer() function reads up to @count bytes from the
+ * buffer @from at offset @ppos into the user space address starting at @to.
+ *
+ * On success, the number of bytes read is returned and the offset @ppos is
+ * advanced by this number, or negative value is returned on error.
+ **/
+ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
+				const void *from, size_t available)
+{
+	loff_t pos = *ppos;
+	size_t ret;
+
+	if (pos < 0)
+		return -EINVAL;
+	if (pos >= available || !count)
+		return 0;
+	if (count > available - pos)
+		count = available - pos;
+	ret = copy_to_user(to, from + pos, count);
+	if (ret == count)
+		return -EFAULT;
+	count -= ret;
+	*ppos = pos + count;
+	return count;
+}
+
+/**
+ * simple_write_to_buffer - copy data from user space to the buffer
+ * @to: the buffer to write to
+ * @available: the size of the buffer
+ * @ppos: the current position in the buffer
+ * @from: the user space buffer to read from
+ * @count: the maximum number of bytes to read
+ *
+ * The simple_write_to_buffer() function reads up to @count bytes from the user
+ * space address starting at @from into the buffer @to at offset @ppos.
+ *
+ * On success, the number of bytes written is returned and the offset @ppos is
+ * advanced by this number, or negative value is returned on error.
+ **/
+ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
+		const void __user *from, size_t count)
+{
+	loff_t pos = *ppos;
+	size_t res;
+
+	if (pos < 0)
+		return -EINVAL;
+	if (pos >= available || !count)
+		return 0;
+	if (count > available - pos)
+		count = available - pos;
+	res = copy_from_user(to + pos, from, count);
+	if (res == count)
+		return -EFAULT;
+	count -= res;
+	*ppos = pos + count;
+	return count;
+}
+
+/**
+ * memory_read_from_buffer - copy data from the buffer
+ * @to: the kernel space buffer to read to
+ * @count: the maximum number of bytes to read
+ * @ppos: the current position in the buffer
+ * @from: the buffer to read from
+ * @available: the size of the buffer
+ *
+ * The memory_read_from_buffer() function reads up to @count bytes from the
+ * buffer @from at offset @ppos into the kernel space address starting at @to.
+ *
+ * On success, the number of bytes read is returned and the offset @ppos is
+ * advanced by this number, or negative value is returned on error.
+ **/
+ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
+				const void *from, size_t available)
+{
+	loff_t pos = *ppos;
+
+	if (pos < 0)
+		return -EINVAL;
+	if (pos >= available)
+		return 0;
+	if (count > available - pos)
+		count = available - pos;
+	memcpy(to, from + pos, count);
+	*ppos = pos + count;
+
+	return count;
+}
+
+/*
+ * Transaction based IO.
+ * The file expects a single write which triggers the transaction, and then
+ * possibly a read which collects the result - which is stored in a
+ * file-local buffer.
+ */
+
+void simple_transaction_set(struct file *file, size_t n)
+{
+	struct simple_transaction_argresp *ar = file->private_data;
+
+	BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
+
+	/*
+	 * The barrier ensures that ar->size will really remain zero until
+	 * ar->data is ready for reading.
+	 */
+	smp_mb();
+	ar->size = n;
+}
+
+char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
+{
+	struct simple_transaction_argresp *ar;
+	static DEFINE_SPINLOCK(simple_transaction_lock);
+
+	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
+		return ERR_PTR(-EFBIG);
+
+	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
+	if (!ar)
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock(&simple_transaction_lock);
+
+	/* only one write allowed per open */
+	if (file->private_data) {
+		spin_unlock(&simple_transaction_lock);
+		free_page((unsigned long)ar);
+		return ERR_PTR(-EBUSY);
+	}
+
+	file->private_data = ar;
+
+	spin_unlock(&simple_transaction_lock);
+
+	if (copy_from_user(ar->data, buf, size))
+		return ERR_PTR(-EFAULT);
+
+	return ar->data;
+}
+
+ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
+{
+	struct simple_transaction_argresp *ar = file->private_data;
+
+	if (!ar)
+		return 0;
+	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
+}
+
+int simple_transaction_release(struct inode *inode, struct file *file)
+{
+	free_page((unsigned long)file->private_data);
+	return 0;
+}
+
+/* Simple attribute files */
+
+struct simple_attr {
+	int (*get)(void *, u64 *);
+	int (*set)(void *, u64);
+	char get_buf[24];	/* enough to store a u64 and "\n\0" */
+	char set_buf[24];
+	void *data;
+	const char *fmt;	/* format for read operation */
+	struct mutex mutex;	/* protects access to these buffers */
+};
+
+/* simple_attr_open is called by an actual attribute open file operation
+ * to set the attribute specific access operations. */
+int simple_attr_open(struct inode *inode, struct file *file,
+		     int (*get)(void *, u64 *), int (*set)(void *, u64),
+		     const char *fmt)
+{
+	struct simple_attr *attr;
+
+	attr = kmalloc(sizeof(*attr), GFP_KERNEL);
+	if (!attr)
+		return -ENOMEM;
+
+	attr->get = get;
+	attr->set = set;
+	attr->data = inode->i_private;
+	attr->fmt = fmt;
+	mutex_init(&attr->mutex);
+
+	file->private_data = attr;
+
+	return nonseekable_open(inode, file);
+}
+
+int simple_attr_release(struct inode *inode, struct file *file)
+{
+	kfree(file->private_data);
+	return 0;
+}
+
+/* read from the buffer that is filled with the get function */
+ssize_t simple_attr_read(struct file *file, char __user *buf,
+			 size_t len, loff_t *ppos)
+{
+	struct simple_attr *attr;
+	size_t size;
+	ssize_t ret;
+
+	attr = file->private_data;
+
+	if (!attr->get)
+		return -EACCES;
+
+	ret = mutex_lock_interruptible(&attr->mutex);
+	if (ret)
+		return ret;
+
+	if (*ppos) {		/* continued read */
+		size = strlen(attr->get_buf);
+	} else {		/* first read */
+		u64 val;
+		ret = attr->get(attr->data, &val);
+		if (ret)
+			goto out;
+
+		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
+				 attr->fmt, (unsigned long long)val);
+	}
+
+	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
+out:
+	mutex_unlock(&attr->mutex);
+	return ret;
+}
+
+/* interpret the buffer as a number to call the set function with */
+ssize_t simple_attr_write(struct file *file, const char __user *buf,
+			  size_t len, loff_t *ppos)
+{
+	struct simple_attr *attr;
+	u64 val;
+	size_t size;
+	ssize_t ret;
+
+	attr = file->private_data;
+	if (!attr->set)
+		return -EACCES;
+
+	ret = mutex_lock_interruptible(&attr->mutex);
+	if (ret)
+		return ret;
+
+	ret = -EFAULT;
+	size = min(sizeof(attr->set_buf) - 1, len);
+	if (copy_from_user(attr->set_buf, buf, size))
+		goto out;
+
+	attr->set_buf[size] = '\0';
+	val = simple_strtoll(attr->set_buf, NULL, 0);
+	ret = attr->set(attr->data, val);
+	if (ret == 0)
+		ret = len; /* on success, claim we got the whole input */
+out:
+	mutex_unlock(&attr->mutex);
+	return ret;
+}
+
+/**
+ * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
+ * @sb:		filesystem to do the file handle conversion on
+ * @fid:	file handle to convert
+ * @fh_len:	length of the file handle in bytes
+ * @fh_type:	type of file handle
+ * @get_inode:	filesystem callback to retrieve inode
+ *
+ * This function decodes @fid as long as it has one of the well-known
+ * Linux filehandle types and calls @get_inode on it to retrieve the
+ * inode for the object specified in the file handle.
+ */
+struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
+		int fh_len, int fh_type, struct inode *(*get_inode)
+			(struct super_block *sb, u64 ino, u32 gen))
+{
+	struct inode *inode = NULL;
+
+	if (fh_len < 2)
+		return NULL;
+
+	switch (fh_type) {
+	case FILEID_INO32_GEN:
+	case FILEID_INO32_GEN_PARENT:
+		inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
+		break;
+	}
+
+	return d_obtain_alias(inode);
+}
+EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
+
+/**
+ * generic_fh_to_dentry - generic helper for the fh_to_parent export operation
+ * @sb:		filesystem to do the file handle conversion on
+ * @fid:	file handle to convert
+ * @fh_len:	length of the file handle in bytes
+ * @fh_type:	type of file handle
+ * @get_inode:	filesystem callback to retrieve inode
+ *
+ * This function decodes @fid as long as it has one of the well-known
+ * Linux filehandle types and calls @get_inode on it to retrieve the
+ * inode for the _parent_ object specified in the file handle if it
+ * is specified in the file handle, or NULL otherwise.
+ */
+struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
+		int fh_len, int fh_type, struct inode *(*get_inode)
+			(struct super_block *sb, u64 ino, u32 gen))
+{
+	struct inode *inode = NULL;
+
+	if (fh_len <= 2)
+		return NULL;
+
+	switch (fh_type) {
+	case FILEID_INO32_GEN_PARENT:
+		inode = get_inode(sb, fid->i32.parent_ino,
+				  (fh_len > 3 ? fid->i32.parent_gen : 0));
+		break;
+	}
+
+	return d_obtain_alias(inode);
+}
+EXPORT_SYMBOL_GPL(generic_fh_to_parent);
+
+/**
+ * generic_file_fsync - generic fsync implementation for simple filesystems
+ * @file:	file to synchronize
+ * @datasync:	only synchronize essential metadata if true
+ *
+ * This is a generic implementation of the fsync method for simple
+ * filesystems which track all non-inode metadata in the buffers list
+ * hanging off the address_space structure.
+ */
+int generic_file_fsync(struct file *file, int datasync)
+{
+	struct inode *inode = file->f_mapping->host;
+	int err;
+	int ret;
+
+	ret = sync_mapping_buffers(inode->i_mapping);
+	if (!(inode->i_state & I_DIRTY))
+		return ret;
+	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
+		return ret;
+
+	err = sync_inode_metadata(inode, 1);
+	if (ret == 0)
+		ret = err;
+	return ret;
+}
+EXPORT_SYMBOL(generic_file_fsync);
+
+/**
+ * generic_check_addressable - Check addressability of file system
+ * @blocksize_bits:	log of file system block size
+ * @num_blocks:		number of blocks in file system
+ *
+ * Determine whether a file system with @num_blocks blocks (and a
+ * block size of 2**@blocksize_bits) is addressable by the sector_t
+ * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
+ */
+int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
+{
+	u64 last_fs_block = num_blocks - 1;
+	u64 last_fs_page =
+		last_fs_block >> (PAGE_CACHE_SHIFT - blocksize_bits);
+
+	if (unlikely(num_blocks == 0))
+		return 0;
+
+	if ((blocksize_bits < 9) || (blocksize_bits > PAGE_CACHE_SHIFT))
+		return -EINVAL;
+
+	if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
+	    (last_fs_page > (pgoff_t)(~0ULL))) {
+		return -EFBIG;
+	}
+	return 0;
+}
+EXPORT_SYMBOL(generic_check_addressable);
+
+/*
+ * No-op implementation of ->fsync for in-memory filesystems.
+ */
+int noop_fsync(struct file *file, int datasync)
+{
+	return 0;
+}
+
+EXPORT_SYMBOL(dcache_dir_close);
+EXPORT_SYMBOL(dcache_dir_lseek);
+EXPORT_SYMBOL(dcache_dir_open);
+EXPORT_SYMBOL(dcache_readdir);
+EXPORT_SYMBOL(generic_read_dir);
+EXPORT_SYMBOL(mount_pseudo);
+EXPORT_SYMBOL(simple_write_begin);
+EXPORT_SYMBOL(simple_write_end);
+EXPORT_SYMBOL(simple_dir_inode_operations);
+EXPORT_SYMBOL(simple_dir_operations);
+EXPORT_SYMBOL(simple_empty);
+EXPORT_SYMBOL(simple_fill_super);
+EXPORT_SYMBOL(simple_getattr);
+EXPORT_SYMBOL(simple_link);
+EXPORT_SYMBOL(simple_lookup);
+EXPORT_SYMBOL(simple_pin_fs);
+EXPORT_SYMBOL(simple_readpage);
+EXPORT_SYMBOL(simple_release_fs);
+EXPORT_SYMBOL(simple_rename);
+EXPORT_SYMBOL(simple_rmdir);
+EXPORT_SYMBOL(simple_statfs);
+EXPORT_SYMBOL(noop_fsync);
+EXPORT_SYMBOL(simple_unlink);
+EXPORT_SYMBOL(simple_read_from_buffer);
+EXPORT_SYMBOL(simple_write_to_buffer);
+EXPORT_SYMBOL(memory_read_from_buffer);
+EXPORT_SYMBOL(simple_transaction_set);
+EXPORT_SYMBOL(simple_transaction_get);
+EXPORT_SYMBOL(simple_transaction_read);
+EXPORT_SYMBOL(simple_transaction_release);
+EXPORT_SYMBOL_GPL(simple_attr_open);
+EXPORT_SYMBOL_GPL(simple_attr_release);
+EXPORT_SYMBOL_GPL(simple_attr_read);
+EXPORT_SYMBOL_GPL(simple_attr_write);